1. Field of the Invention
The present invention relates to a traffic checking/state monitoring system of a forwarding plane (packet transfer function through full wire not by software but by packet transfer only hardware) of a router which constitutes a Layer 2-Virtual Private Network (L2-VPN).
2. Description of the Related Art
In recent years, at corporations or the like whose bases are dispersed to several places, a form has increasingly been taken to interconnect the bases of the places through an Internet network, and to virtually build one local area network (L2-VPN). This has been accompanied by a rapid increase in the number of providers for rendering L2-VPN connection services.
The L2-VPN is a VPN through which the provider offers a layer 2 connection between customer sites. In the L2-VPN, a provider network which renders VPN services interconnects user networks equivalent to the customer sites.
A provider edge router (PE) is arranged in a boundary between the provider network and the user network. The Provider edge router relays communication from the user network, and transfers it into the provider network. The provider which renders connection services of Layer 2 always monitors whether the user network can communication with the opposite user network or not through the Provider edge router.
Additionally, in the case of adding a new communication device in the user network, the provider checks whether the new communication device can communicate with a communication device in the opposite user network or not through the Provider edge router by a control plane (series of control operations for signaling, saving and updating of routing information, and setting of a forwarding path).
However, in actual communication between the user networks, data transfer is executed by a forwarding plane. Consequently, it is necessary to check, not only in the case of the control plane but also in the case of the forwarding plane, whether actual user communication is normal or not.
Generally, as shown in FIG. 20, a recent router includes a packet transfer control unit different from a protocol control unit. Thus, to enable the Provider edge router that includes the protocol control unit and the packet transfer control unit to check normality of communication with the opposite user network, the Provider edge router must actually send a communication packet from the user network side to the opposite user network. Moreover, using a packet internet grouper (ping), traffic checking must be carried out by a terminal connected to the Provider edge router directly or through an L2 switch.
The provider network may be constituted by using Multi Protocol Label Switching (MPLS). FIG. 21 shows an example of a provider network to which the MPLS is applied. In this case, there are a plurality of packet reaching paths between a Provider edge router (e.g., PE-1) and an opposite Provider edge router (e.g., PE-2).
Additionally, in the provider network, depending on Equal Cost Multi-Path (ECMP) services, each router that relays a packet may use a plurality of paths for load dispersion. Accordingly, there is a large amount of a forwarding plane in the provider network.
In the traffic checking that uses the ping as described above, a Media Access Control (MAC) address of the terminal is used for reaching path determination. Thus, a part of the forwarding plane actually used by a user cannot be checked. Consequently, to check normality of all the forwarding planes used by the user, the following means (1) or (2) must be employed.
(1) All the terminals in the user network execute communication of ping or the like with all the terminals in the opposite user network, and checking is carried out at each terminal in the user network. In an example shown in FIG. 21, there are terminals T-1 and T-2 in the user network A, and there are terminals T-3 and T-4 in the user network B. The terminal T-1 of the user network A transmits a ping packet to each of the terminals T-3 and T-4 of the opposite user network B. The terminal T-2 also transmits a ping packet to each of the terminals T-3 and T-4. The terminal T-1 can check normality of a forwarding plane on a transmission route of each ping packet which reaches each of the terminals T-3 and T-4 from the terminal T-1 by receiving a response packet of each ping packet. The terminal T-2 can check normality of a forwarding plane on a transmission route of each ping packet which reaches each of the terminals T-3 and T-4 from the terminal T-2 by receiving a response packet of each ping packet.
(2) Testing devices that can freely create, transmit and receive communication packets are installed in the user network and the opposite user network, communication is carried out for all forwarding planes between the testing devices, and checking is executed at the two testing devices.
However, in the case of the means (1), the terminals in the user network are under user's management. Consequently, the provider cannot freely operate the terminals. Besides, for each addition of a terminal in the user network, the added terminal must execute ping for each terminal in the opposite user network. Consequently, enormous management costs are necessary.
Additionally, in the case of the means (2), there is a problem in that it is difficult to install a testing device prepared by the provider for the user network therein. Since expensive testing devices are necessary in all the user networks, enormous equipment costs are necessary.
Therefore, in the present circumstances, a method is employed which executes ping or the like at the Provider edge router, and checks a forwarding plane of a core router (router in provider network: routers R-1 to R-4 in FIG. 21) only. Alternatively, a method is employed which checks traffic of only a part of a forwarding plane including the edge router by a small number of terminals connected to the Provider edge router. In other words, normality of all the forwarding planes through which user's traffic passes is not carried out. In the present circumstances, monitoring of normality is executed only for a control plane.
Incidentally, as a prior art concerning the present invention, for example, there are a monitoring device, a monitoring method and a recording medium disclosed in Patent document 1.
[Patent document 1] JP 2001-326638 A
As described above, the normality checking of the forwarding plane in the prior art has been carried out only for the transfer by the core router. Alternatively, the normality checking of the forwarding plane has been carried out only for a part of routes in all the forwarding planes. Consequently, when an abnormality occurs in communication of the forwarding plane while the control plane is normal, a maintenance engineer cannot recognize the abnormality of the forwarding plane, and early discovery of the communication abnormality is impossible.